Expose classifySmallText()

I have two use cases for this. First, one may want to be sure that
the result is what lucene returned, not the merge of separately analyzed
chunks of text. Second, one may want to control the size of the chunks,
rather than letting TMFCore decide where to split.
Merge pull request #15 from bassosimone/feature/expose_classify_short

Expose classifySmallText()